$${V = H_{1}\left( \frac{D_{1}}{2} \right)^{2}\pi - \left( H_{1} - H_{2} \right)\left( \frac{D_{2}}{2} \right)^{2}\pi - H_{2}\left( \frac{D_{3}}{2} \right)^{2}\pi\backslash n}{\ \ = \frac{1}{4}\pi\left( H_{1} \bullet {D_{1}}^{2} - \left( H_{1} - H_{2} \right){D_{2}}^{2} - H_{2} \bullet {D_{3}}^{2} \right)}$$